Method in connection with a roof drainage apparatus and a roof drainage apparatus

ABSTRACT

The invention relates to a method in connection with a roof drainage apparatus and a roof drainage apparatus. The invention comprises a trough (2) recessed in a roof structure (1), an opening (3) arranged in the bottom of the trough, a water-outlet tube (4) joined to the opening and a means (5) for changing an open water flow into a closed flow when the water flow is increasing. For intensifying the drainage, an element (6) is positioned in the water-outlet tube (4) at a throat after the opening (3), by means of which element the cross-sectional area of the water-outlet tube (4) is regulated in such a manner that the shape of the cross-section of the water-outlet tube (4) remains substantially unchanged at the regulation.

BACKGROUND OF THE INVENTION

The invention relates to a method in connection with a roof drainageapparatus, in which a water flow, when increasing, is changed from anopen flow into a closed flow and directed into a water-outlet tubethrough an opening arranged in the bottom of a trough recessed in a roofstructure. The invention also relates to a roof drainage apparatus.

Such solutions are well-known at present. As an example of prior artsolutions can be mentioned an apparatus disclosed in Finnish Patent70446. In this known solution the opening is arranged directly in theroof level. The means changing open flow into closed flow comprise aplate positioned above the opening, the size of the plate and itsdistance from the roof level being dimensioned according to criteriacausing closed flow.

Another example of a prior art solution is an apparatus disclosed inFinnish Patent 75394. This apparatus utilizes the same basic principlecausing closed flow as the apparatus according to Finnish Patent 70446.However, in the apparatus according to Finnish Patent 75394, the openingis arranged in a trough recessed in the roof structure and not directlyin the roof level as in Finnish Patent 70446 mentioned above.

The above-mentioned solutions work very well in principle, but drawbackshave nevertheless been observed especially in connection with largeroofs provided with several roof outlets joined to the same tube system.These drawbacks are due to the fact that it is difficult to provideseparate roof outlet branches with correct flow resistances. In theevent that the separate roof outlet branches cannot be provided withcorrect flow resistance, the system does not function in the bestpossible manner, and in the worst case, the system does not function atall. An additional inconvenience is also that tubes in differentdiameters are available to a relatively restricted extent, and it istherefore often necessary in practice to make compromises when choosingtubes. Further inconveniences are caused by the fact that it has notbeen possible to regulate the flow resistances of the separate roofoutlet branches after the installation of the tube system. It shall benoted that the system is rather sensitive to blockages caused byimpurities, so that flaps or the like of whatever kind cannot be used,if a reliable function of the system is desired in all circumstances.

SUMMARY OF THE INVENTION

The object of the invention is to provide a method and an apparatus bymeans of which the drawbacks of the prior art technique can beeliminated. This has been achieved by means of the solution of theinvention. The method according to the invention is characterized inthat the cross-sectional area of the water-outlet tube is regulated in athroat after the opening arranged in the bottom of the trough in such amanner that the shape of the cross-section remains substantiallyunchanged. On the other hand, the drainage apparatus according to theinvention is characterized in that an element is positioned in thewater-outlet tube at the throat after the opening, by means of whichelement the cross-sectional area of the water-outlet tube can beregulated in such a way that the shape of the cross-section of thewater-outlet tube remains substantially unchanged at the regulation.

In comparison with the prior art technique, the primary advantage of theinvention is that the flow resistances of the separate roof outletbranches can be regulated after the installation in a rather simplemanner. It is thus possible to regulate the system to functionpractically optimally in each particular roof structure. A furtheradvantage is that flow resistances can be regulated within a very widerange, which makes the system function reliably even in very difficultcases. Flow resistance can be changed within a range of 0 up to 90%. Anadvantage of the invention is also that a regulating element can easilybe formed such that impurities do not stick to it, and therefore, nodetrimental blockage can occur. It is also simple to arrange a doublesieve in the apparatus of the invention, which means easy cleaning, forinstance, and an elimination of difficulties caused by blockage. Stillan advantage of the invention is its simplicity, due to which thedrainage apparatus of the invention functions reliably, the need ofmaintenance is little and the invention can be introducedadvantageously.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in the following by means of preferableembodiments of the invention shown in the enclosed drawing, in which

FIG. 1 shows a side view of a drainage apparatus according to theinvention in principle,

FIG. 2 shows a substantial detail of the apparatus of FIG. 1 after theregulation of a flow resistance and

FIG. 3 to 6 show different alternative embodiments of the apparatusaccording to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a side view of one preferable embodiment of a roof drainageapparatus according to the invention in principle. Reference numeral 1indicates a roof structure of a building. Reference numeral 2 of FIG. 1indicates a trough, in the bottom of which is arranged an opening 3. Tothe opening 3 is joined a water-outlet tube 4, by means of which thewater is led to a place desired. Reference numeral 5 of FIG. 1 indicatesgenerally means for changing an open water flow into a closed flow whenthe water flow is increasing.

The facts mentioned above belong to a technique fully conventional toone skilled in the art, and therefore, these facts are not presentedmore accurately in this connection. It is only stated in general thatfor instance changing open flow into closed flow and the details of theapparatus and the principles used thereby appear e.g. from FinnishPatent 70446. As to these facts, reference is made to theabove-mentioned Finnish Patent as prior art.

The substantial feature of the invention is that the cross-sectionalarea of the water-outlet tube 4 is regulated in a throat after theopening 3 arranged in the bottom of the trough 2 in such a manner thatthe shape of the cross-section remains substantially unchanged. Thecross-sectional area can be regulated by throttling the water-outlettube 4, preferably along the whole perimeter. The regulation of thecross-section of the water-outlet tube 4 can be carried out for instanceby means of an element 6 positioned at the throat. The element 6 extendsover the whole perimeter of the water-outlet tube 4 and throttles thewater-outlet tube 4 along its whole perimeter. In the embodiment of FIG.1 the element 6 is an annular part of an elastic material, such asrubber, which is arranged to expand inwards at axial compression andthus to throttle the cross-sectional area of the water-outlet tube 4.The axial compression of the element 6 can take place by means of anannular compression part 7, for instance. The axial movement of thecompression part can be provided e.g. by means of a thread structure.Throttling the water tube is seen especially well from FIG. 2, whichshows the throat of the water-outlet tube 4 of the embodiment accordingto FIG. 1 after the regulation of the flow resistance, i.e. afterthrottling the water tube. From FIG. 2 can be seen that the annularcompression part 7 has moved downwards and compressed the element 6, andthen the element has expanded inwards and throttles thus thewater-outlet tube 4 and increases the flow resistance. The flowresistance can naturally be reduced by turning the compression part 7 inthe opposite direction, in which case the compression part moves upwardsand the element can return towards the shape according to FIG. 1. Bythis arrangement it is possible to regulate the size of the flow openingof the water-outlet tube 4 in such a way that the cross-sectional areaof the water-outlet tube remains unchanged, i.e. a round cross-sectionremains round in spite of regulation etc. The regulation takes place bychanging the value of single resistance. Let the single resistance valueof the whole apparatus without throttling be ζ₁. The pressure losscaused by the flow is then ##EQU1## in which Δp₁ =pressure loss mm watercolumn, w₁ =speed in the throat m/s, g=acceleration of gravity 9,81m/s², λ=volume weight of water kg/m³ =1000. If a throttling point isarranged in the throat, the single resistance value of throttling ζ₂ is,depending on inlet and outlet roundings and expressed for the speed atthe throttling point, 0,5÷1,6. The pressure loss of throttling is##EQU2## in which w₂ =speed at the throttling point. Δp₂ is expressed asa function of the speed w₁. ##EQU3## because cross-section×speed isequal at each point, d₁ =diameter of water-outlet tube before throttlingpoint, d₂ =diameter of water-outlet tube at throttling point, from which##EQU4## w₂ is substituted in the formula of the pressure loss ofthrottling ##EQU5## The total resistance of the roof outlet is the totalof the partial resistances; ##EQU6## from which appears that the singleresistance value of a roof outlet provided with throttling is ##EQU7##Example: Let the single resistance value of a roof outlet withoutthrottling be ζ₁ =0,3 and that with throttling for its own diameter (d₂)ζ₂ =0,5 and the inner diameter of the throat d₁ =50 mm and that ofthrottling d₂ =10 mm. Then ##EQU8## The pressure losses are throttledand unthrottled as follows

    ______________________________________                                                 unthrottled    throttled                                             w m/s    Δp mm water column                                                                     Δp mm water column                              ______________________________________                                        0,3      1,38           1435                                                  0,5      3,82           3987                                                  1        15,29          15949                                                 ______________________________________                                    

Consequently, by throttling according to the invention it is possible toprovide very large additional pressure losses for balancing the flowresistances of the separate branches.

The shape of the cross-sectional surface of the element can vary. In theembodiment of the FIGS. 1 and 2 the cross-section is oval. In theexample of FIG. 3 the cross-section of an element 16 is round. As to therest, the embodiment of FIG. 3 corresponds to the embodiment of theFIGS. 1 and 2. In the embodiment of FIG. 5 the cross-sectional surfaceof an element 26 is a rectangle. As to the rest, the example of FIG. 5corresponds to the embodiments of the FIGS. 1 to 3.

FIG. 6 shows an embodiment, in which the element comprises two parts, anelastic annular means 36a and a sleeve 36b capable of contracting andexpanding. The sleeve 36b can for instance be a tube bent of a plate,the edges of which are not fastened together but only bent in such a waythat the free longitudinal edges of the plate are capable of movingoverlappingly at the regulation. As to the rest, the embodiment of FIG.6 corresponds to the preceding embodiments. Identical reference numeralshave been used for respective parts in the FIGS. 1 to 3, 5 and 6,because the solutions are similar as far as those parts are concerned.

FIG. 4 shows an embodiment in which an element 46 is a part to be chosenaccording to the cross-sectional surface desired for a water-outlet tube14, i.e. the element 46 is detached for the regulation of flowresistance and replaced by an element throttling the cross-sectionalarea of the water-outlet tube in a manner desired. In FIG. 4 is markedwith broken lines one example of how the element in question can be. InFIG. 4, the reference numeral 12 indicates the trough and the referencenumeral 13 the opening to which the water-outlet tube 14 is joined.Means for the provision of closed flow, for instance, are not shown inFIG. 4 at all, nor in the FIGS. 2, 3, 5 and 6. These means can naturallybe e.g. means according to FIG. 1.

All above-mentioned solutions make it possible to regulate the flowresistance also after the installation, through which the function ofthe whole water-outlet system can be made very advantageous.

The embodiments above are not intended to restrict the invention, butthe invention can be modified quite freely within the scope of theclaims. It is thus clear that the details of the apparatus according tothe invention can also be different from the ones shown in the Figures.The annular element does not necessarily need to be made of rubber, butthis element can also consist e.g. of a spring element throttling thewater-outlet tube when tightened. The tightening can take place in anydirection. The element throttling the water-outlet tube can also bemanufactured of more than one material; a closed shell manufactured e.g.of rubber or plastic and containing liquid or gas is a fully possiblesolution. Sieve structures and structures causing closed flow can be anysolutions obvious to persons skilled in the art. In this respect, theexample of FIG. 1 is to be understood as an example in principle and notas an example of some particular specified solution.

I claim:
 1. A method for controlling fluid flow along a roof having atrough recessed in the roof comprising the steps of:providing adeformable annular element in an outlet passage extending downward fromthe trough, the annular element defining a throat portion with across-sectional area and a cross-sectional shape; and moving acompression member, mounted to the outlet passage, in an axial directionwhile in contact with the annular element thereby deforming the annularelement to adjust the cross-sectional area of the throat portion withoutsubstantially changing the cross-sectional shape of the throat portion.2. The method of claim 1 wherein the deforming step includes throttlingthe outlet tube to regulate the cross-sectional area of the throatportion.
 3. The method of claim 2 wherein the throat portion has aperimeter, the throttling step including throttling the outlet tubealong the entire perimeter of the throat portion.